Description
Long life SQ (Special Quality) ECC81 tubes !
This is an early pair 6201 Philips Miniwatt tubes, produced by the Philips subsidiary Valvo in april 1962 in the Hamburg Valvo factories. The pair has a halo getter, a half box plate structure, and gold pins, see pictures. Healthy tubes with NOS specs! Tubes with matching triode systems; see test results. This is the long life, tight tolerance version of the ECC81/12AT7. This tube type was made exclusively for governmental institutions and manufacturers of high precision gear. The SQ marking means Special Quality! Overall, the 6201 tube is a step up from the standard 12AT7.
Sonics
Note from the WEB: These tubes are characterized by an impressive open “air” at the top end. The soundstage is large. The midrange is flat, and the bass is tight and accurate. These tubes have a fine sense of dynamics, and most are impressively quiet. These are not “very warm sounding” tubes, and to some ears their lower of midrange warmth may be interpreted as transparent/bright. I tend to think of them as accurate, and their clean, focused sonic image is astonishing. They are absolutely incredible tubes that will never be made again!
Valvo’s Hamburg production has a good reputation among tube enthusiasts. Experiences with this 6201 SQ mainly point to:
-
- A very open and detailed high.
- A nice layered sound image.
- A natural representation of voices.
- A tight layer without excessive thickness.
- An excellent placement of instruments.
This is typically a tube for someone who loves detail, spaciousness and a natural rendering, without excessive heat or coloring. The Valvo is described by some listeners as a middle ground between the fast, lively Siemens and the somewhat smoother, warmer Mullard
Test results*
The tubes have been tested carefully with the official factory test set-up and our sophisticated test equipment. Please read our tube testing page for the ECC81 tube family. The measurement data below show that these tubes are perfectly matched to each other and are internally balanced. And meet the factory specifications of a new/NOS tube very wel. Tube to tube match and internal balance for all tubes is excellent. .
| Valve
V151
|
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
10,8 / 10,3 mA
6,3 /6,4 mA/V OK |
= NOS / NOS
= NOS / NOS
|
| Valve
V152
|
Ia (plate current):
Transconductance (Gm): Gas test, Shorts test: |
10,9 / 11,3 mA
6,1 /6,3 mA/V OK |
= NOS / NOS
= NOS / NOS
|
Where NOS is : Ia = 7 to 14 mA, Gm= 4,5 to 6,5 mA/V.
* For test methods and factory specification read the tube testing page.
Short description
| Tube type | 6201 |
| Quantity of Tubes | One pair |
| Brand | Philips Miniwatt |
| Manufactured in | Valvo factory, Hamburg Germany |
| Etch code | Df6 D 2D1 & Df6 D 2D2 (1962) |
| Construction | Half box plates, gold pins |
| Getter Construction | Halo getter; see pictures |
| Print Condition | See pictures |
| Box included | Generic Philips factory box |
| Equivalent tubes: | 12AT7, ECC81, 12AT7WA, ECC801S |
| General test results | NOS |
